This project is composed of two parts. The aim of the first part is to examine the mechanical properties of human respiratory muscles, to compare them with non-respiratory muscles, and to determine the effects of age, status of musculature, nutritional state and chronic respiratory loading (owing to disease) upon them. Muscle biopsies approximately 2.0 by 0.3 x 0.3 cm in size will be obtained during regularly scheduled surgery for other purposes after informed consent has been obtained. Multiple respiratory muscles will be tested, and the following determinations will be made: 1) isometric twitch time; 2) isometric force-frequency relationship; 3) isometric twitch-tetanic tension ratio; 4) length-tension relationship; 5) force-velocity relationship; 6) load-extension relationship of series elastance; 7) intrinsic strength of contractile material; 8) histochemical fiber typing. Muscles to be tested will be 1) diaphragm, 2) intercostals, 3) scaleni, 4) sternomastoids, 5) abdominal muscles (internal and external oblique and transversus) 6) a slow extremity muscle (soleus) and 7) fast extremity muscles (bicepts brachii, gastrocnemius, forearm flexors). The aim of the second part of the project is to compare respiratory muscle function and deployment and the strategies of breathing in acute airways obstruction (asthma) versus chronic airways obstruction (C.O.P.D.). Patients would be followed with serial physiologic observations beginning with admission to a respiratory intensive care unit in acute distress and continuing through recovery until discharge. Measurements will include respiratory pressures (esophageal, gastric, transdiaphragmatic and airway occlusion), thoracoabdominal motion and dimensions, multiple respiratory muscle electromyograms, respiratory volumes and air flow and arterial blood gases. EMG's of the following muscles will be recorded: 1) diaphragm, 2) intercostals, 3) scaleni, 4) sternocleidomastoids, and 5) abdominal obliques. Data analysis will concentrate on characterizing and comparing patterns of respiratory muscle deployment, tonic versus phasic activity of the various muscles, breathing patterns, and breathing strategies in the two types of airway obstruction.